Process for the production of unbranched polyarylene sulfides of improved color quality and improved color stability

Abstract

The invention relates to a process for the production of linear, unbranched polyarylene sulfides from aromatic dichlorine compounds and alkali sulfides in tetra-alkylated, cyclic ureas as the reaction medium.

We claim: 
     
       1. A process for the production of high molecular weight polyarylene sulfides from (a) 50 to 100 mol-% aromatic dihalogen compounds corresponding to the formula ##STR4## and 0 to 50 mol-% aromatic dihalogen compounds corresponding to the formula ##STR5## in which the X's are halogen atoms selected from chlorine and bromine atoms, in the meta- or para-position to one another and   the R 1  's may be the same or different and represent hydrogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl; two substituents R 1  in the ortho position to one another are attached to form an aromatic or heterocyclic ring and at least one substituent R 1  is not hydrogen, and   (b) alkali sulfides, optionally together with alkali hydroxides, and molar ratio of aromatic dichlorine compounds to sulfides being in the range from 0.85:1 to 1.15:1, wherein N,N'-dialkylated cyclic ureas corresponding to formula (III) ##STR6## in which R 1  and R 2  one alkyl or aryl     R 3  and R 4  represent hydrogen (H) or C 1  -C 22  alkyl and   n is the number 2, 3 or 4, and in that the molar ratio of alkali sulfides to the organic solvent is in the range from 1:2 to 1:5, anhydrous starting materials are introduced first and heated to at least 150° C. and aqueous materials and residues of the anhydrous starting materials are introduced in the form of a solution or melt or in solid form in such a way that the water introduced is removed from the reaction mixture by distillation and the reaction is subsequently carried out at temperatures in the range from 210° C. to 270° C. optionally under a slight excess pressure.     
     
     
       2. A process as claimed in claim 1, characterized in that 1,4-dichlorobenzene is used as the aromatic dihalogen compound of formula (I). 
     
     
       3. A process as claimed in claim 1, characterized in that N,N'-dimethyl-2-imidazolidinone is used as solvent. 
     
     
       4. A process as claimed in claim 1, characterized in that the condensation is carried out at an excess pressure of 0.3 to 3 bar.